# Multiwavelength study of VHE emission from Markarian 501 using TACTIC observations during April-May, 2012

Source: [Multiwavelength study of VHE emission from Markarian 501 using TACTIC observations during April-May, 2012](<https://www.sota2.com/research/paper/68fa35211e209131ce89ef64>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-10-24T21:05:12.131Z

Authors: P Chandra, K K Singh, R C Rannot, K K Yadav, H Bhatt, A K Tickoo, B Ghosal, M Kothari, K K Gaur, A Goyal, H C Goyal, N Kumar, P Marandi, N Chouhan, S Sahayanathan, K Chanchalani, N K Agarwal, V K Dhar, S R Kaul, M K Koul, R Koul, K Venugopal, C K Bhat, C Borwankar, J Bhagwan, A C Gupta

Published: 2017-01-18T03:54:46.000Z

## Abstract

We have observed Markarian 501 in Very High Energy (VHE) gamma-ray wavelength band for 70.6 hours from 15 April to 30 May, 2012 using TACTIC telescope. Detailed analysis of $\\sim$66.3 hours of clean data revealed the presence of a TeV $\\gamma$-ray signal (686$\\pm$77 $\\gamma$-ray events) from the source direction with a statistical significance of 8.89$\\sigma$ above 850 GeV. Further, a total of 375 $\\pm$ 47 $\\gamma$-ray like events were detected in 25.2 hours of observation from 22 - 27 May, 2012 with a statistical significance of 8.05$\\sigma$ indicating that the source has possibly switched over to a relatively high gamma-ray emission state. We have derived time-averaged differential energy spectrum of the state in the energy range 850 GeV - 17.24 TeV which fits well with a power law function of the form $dF/dE=f\_{0}E^{-\\Gamma}$ with $f\_{0}= (2.27 \\pm 0.38) \\times 10 ^{-11} $ photons cm$^{-2}$ s$^{-1}$ TeV$^{-1}$ and $\\Gamma=2.57 \\pm 0.15$. In order to investigate the source state, we have also used almost simultaneous multiwavelength observations viz: high energy data collected by $\\it{Fermi}$-LAT, X-ray data collected by $\\it{Swift}$-XRT and MAXI, optical and UV data collected by $\\it{Swift}$-UVOT, and radio data collected by OVRO, and reconstructed broad-band Spectral Energy Distribution (SED). The obtained SED supports leptonic model (homogeneous single zone) for VHE gamma-ray emission involving synchrotron and synchrotron self Compton (SSC) processes.

## Recorded benchmark results

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/1701.04935>)

[PDF](<https://arxiv.org/pdf/1701.04935.pdf>)